This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2005-0032764, filed on Apr. 20, 2005 in the Korean Intellectual Property Office, the entire disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus having a power controlling device that controls power supplied to a plurality of color developers.
2. Description of the Related Art
Image forming apparatuses print a desired image by receiving a digital image signal and forming an electrostatic latent image on a photosensitive medium coated with a conductive material by using an exposure unit such as a laser scanning unit. The electrostatic latent image is develop into a toner image using toner by transferring the toner image to a recording medium, and fusing the toner image on the recording medium by applying heat and pressure thereto.
Image forming apparatuses generally are classified into dry and wet apparatuses according to a state of toner and carrier being used. Furthermore, the dry apparatuses can be classified into a 1-component developing unit and a 2-component developing unit.
In the 1-component developing unit, an image is formed using only toner. In the 2-component developing unit, an image is formed using a mixture of toner.
In the 1-component developing unit, the toner is provided to the photosensitive medium to develop the toner image. The toner remaining on a surface of the photosensitive medium is removed by a cleaning blade and collected by a collecting unit for reuse. In the 2-component developing unit, the carrier is collected without being provided to the photosensitive medium and only the toner particles are provided to the photosensitive medium to develop the toner image. As a result, the toner particles remaining on the surface of the photosensitive medium are removed by the cleaning blade and collected by the collecting unit for reuse. The above descriptions relate to a case of forming a black and white image. It is difficult to reuse the toner remaining on the photosensitive medium when a color image is formed, because a color toner image on the surface of the photosensitive medium is a mixture of toners of various colors.
In order to form a color image, an image forming apparatus needs four toner cartridges, such as, yellow (Y), magenta (M), cyan (C), and black (K). Developing rollers provided in each of the four toner cartridges supply toners to an electrostatic latent image formed on a photosensitive medium, and develops the electrostatic latent image into a toner image by supplying the toners to the electrostatic latent image.
The developing rollers provided in each of the four toner cartridges are actuated by a driving motor. Since the developing rollers do not need to operate simultaneously, an electrical clutch is used to power the developing rollers selectively.
However, such electrical clutch is expensive and increases the overall size of the image forming apparatus. In addition, the electrical clutch frequently malfunctions and does not operate precisely.
Accordingly, there is a need for an improved image forming apparatus that is reduced in size and has a power controlling device that controls power to the toner cartridges.